The invention concerns an insulating refractory material, particularly suited for the manufacture of articles for the transfer of a molten metal, such as troughs, feeding channels, ladles or like vessels, furnace liners and like apparatus. For applications of this type, the thermal conductivity of the refractory material is of primary importance. Heretofore, in order to compensate the heat losses during molten metal transport, the molten metal was superheated to a temperature above that required for its subsequent casting or maintained at the desired casting temperature by supplying heat so that the melt arrives at its destination at the desired temperature. In order to reduce heat losses, currently used transfer elements such as pouring troughs, usually have two layers of thermal insulation applied to the external surfaces thereof.
The existing receptacles and the troughs could be produced of fused or vitreous silica. This material offers numerous advantages. In particular, it is chemically inert relative to numerous molten metals, such as aluminum, copper, steel, zinc and their alloys. The non-wetability of fused silica also makes it possible to avoid the coating or other surface preparation operations that must be provided in the case of most other refractory materials. The relatively low coefficient of thermal expansion also provides fused silica with excellent thermal shock properties. Its excellent cohesion and low porosity precludes the loosening of surface particles by erosion due to the liquid metal.
Nevertheless, a refractory material such as fused silica has a relatively high coefficient of thermal conductivity, on the order of about 0.7 W/mK at a temperature of 700.degree. C., which makes the material unattractive as a transfer surface for molten metal due to the rapid heat loss which occurs therethrough.